Flexible double-sided electrode sheet and method for manufacturing flexible double-sided electrode sheet

Abstract

This flexible double-sided electrode sheet (5) has at least a flexible insulating resin sheet (2), an electrode portion (P) including a pair of electrodes (1) arranged at opposing positions on the front and back sides of the insulating resin sheet (2), and a connection portion (Q1) including a connection wiring (3) embedded in the insulating resin sheet (2) and connecting the pair of electrodes (1). The electrode portion (P) and the connection portion (Q1) are arranged so as not to overlap within the planar area of the insulating resin sheet (2). The flexible double-sided electrode sheet (5) has high durability such that the electrode portion (P) is not damaged or detached even when bent or stretched, and sufficient conductivity is maintained.

Description

Flexible double-sided electrode sheet and method for manufacturing the same

[0001] The present invention relates to a thin, flexible electrode sheet having electrodes on both sides, and more particularly to a double-sided electrode sheet that has excellent resistance to deformation such as bending and stretching.

[0002] Double-sided electrode elements in which conductors are disposed on both sides of an insulating layer have been known for various applications, and various configurations have been proposed. For example, a pressure-sensitive sensor sheet having a pair of electrodes on both sides of a flexible sheet (Patent Document 1), an inspection jig having a flexible film and an electrode film that penetrates the flexible film and connects the upper and lower sides (Patent Document 2), and a patch having electrodes formed by printing conductive ink on both sides of a flexible substrate, with the electrodes on the front and back sides electrically connected via through holes (Patent Document 3) have been disclosed.

[0003] When electrodes are provided on both sides of a substrate such as a flexible sheet, bending or stretching the sheet can easily cause the electrode parts to break or fall off, resulting in insufficient conduction. Therefore, there is a need for the development of a double-sided electrode sheet that can adequately maintain conduction without causing the electrode parts to break or fall off even when bent or slightly stretched.

[0004] JP 2018-124079 A JP 2009-156737 A International Publication WO2011 / 099512

[0005] An object of the present invention is to develop a highly durable flexible double-sided electrode sheet that maintains sufficient electrical continuity without causing damage or falling off of the electrode portions even when bent or stretched.

[0006] As a result of extensive research, the inventors discovered that the above problem could be solved by arranging the wiring connecting the front electrode and the back electrode at a position away from the electrode portion, and thus completed the present invention.

[0007] That is, the present invention relates to the following flexible double-sided electrode sheet and a manufacturing method thereof: (1) A flexible double-sided electrode sheet comprising at least a flexible insulating resin sheet, electrode portions including a pair of electrodes embedded in opposing positions on the front and back sides of the insulating resin sheet so that their surfaces are exposed, and a connection portion including a connection wiring embedded in the insulating resin sheet and connecting the pair of electrodes, wherein the electrode portions and the connection portion do not overlap within a planar region of the insulating resin sheet.

[0008] (2) The flexible double-sided electrode sheet according to (1), wherein the pair of electrodes are arranged on the front and back sides of the insulating resin sheet with at least a portion of the electrodes exposed.

[0009] (3) The flexible double-sided electrode sheet according to (1), wherein the electrode portion has a structure consisting of at least three layers including a front electrode, a back electrode, and an intermediate insulating resin layer disposed between the front electrode and the back electrode. (4) The flexible double-sided electrode sheet according to (1), wherein the thickness of the flexible insulating resin sheet is 560 μm or less, and the thickness of the intermediate insulating resin layer is 260 μm or less.

[0010] (5) The flexible double-sided electrode sheet according to (4), wherein the length (mm) of the electrode portion / thickness (mm) of the intermediate insulating resin layer is 350 or less. (6) The flexible double-sided electrode sheet according to (1), wherein the flexible insulating resin sheet is made of acrylic resin.

[0011] (7) The flexible double-sided electrode sheet according to (1), wherein at least the electrodes and the connecting wires are formed from a conductive material containing silver.

[0012] (8) A method for producing a flexible double-sided electrode sheet according to any one of (1) to (7), comprising at least the following steps A to E: A: a step of forming a back-side insulating resin layer that constitutes the back side of the flexible insulating resin sheet on a release substrate; B: a step of forming back-side electrodes and wiring; C: a step of forming an intermediate insulating resin layer; D: a step of forming front-side electrodes and wiring; and E: a front-side forming step of forming a front-side insulating resin layer that constitutes the front side of the flexible insulating resin sheet.

[0013] (9) The method for producing a flexible double-sided electrode sheet according to (8), wherein steps A to E include a step of forming a pattern by a screen printing method or an inkjet method.

[0014] The flexible double-sided electrode sheet of the present invention has a pair of electrodes (electrode pair) embedded in opposing positions on both sides of an extremely thin insulating resin sheet so that the surfaces are exposed, and the electrode pair is connected to each other by connecting wiring that is provided so as not to overlap the electrode portions, ensuring electrical continuity. With this structure, even if the sheet is bent or stretched, the electrode portions will not be damaged or removed, thereby maintaining high electrical conductivity.

[0015] The flexible double-sided electrode sheet of the present invention is suitable for use as a bioelectrode in close contact with the skin of the human body to detect biosignals, or for ensuring the conductivity of moving parts in various industries such as the environmental and architectural fields. It can also be suitably used as an electrode for the examination and treatment of organs such as the heart.

[0016] FIG. 1 is a plan view schematically showing an example of a flexible double-sided electrode sheet of the present invention; FIG. 2 is a cross-sectional view schematically showing an example of a flexible double-sided electrode sheet of the present invention; FIG. 3 is a cross-sectional view schematically showing an example of a flexible double-sided electrode sheet of the present invention; FIG. 4 is a cross-sectional view schematically showing an example of a manufacturing process for a flexible double-sided electrode sheet of the present invention; FIG. 5 is a cross-sectional view schematically showing an example of a conventional double-sided electrode sheet; FIG. 6 is a plan view (exterior view seen from above) schematically showing a flexible double-sided electrode sheet produced in Example 1; FIG. 7 is a cross-sectional view schematically showing a flexible double-sided electrode sheet produced in Example 1.

[0017] I. Flexible Double-Sided Electrode Sheet The flexible double-sided electrode sheet of the present invention has a flexible insulating resin sheet as a base material and at least an electrode portion within its planar region. The electrode portion includes a pair of electrodes (electrode pair) consisting of a front electrode and a back electrode embedded in opposing positions on both sides of the insulating resin sheet so that the surfaces are exposed. The front electrode and the back electrode are connected by a connection wiring (conductive wiring) for connecting them and ensuring conductivity. In addition, wiring (main wiring) for connection to an external system is usually extended from the electrodes.

[0018] An example of a flexible double-sided electrode sheet of the present invention is shown schematically in Figures 1 and 2. Figure 1 is a plan view of the front side of the flexible double-sided electrode sheet seen from directly above, and Figure 2 is a cross-sectional view of the flexible double-sided electrode sheet cut along the main wiring extending from the electrodes.

[0019] 1 and 2, 5 denotes a flexible double-sided electrode sheet, 1a denotes a front electrode, 1b denotes a back electrode, 2a, 2b, and 2c denote a front insulating resin layer, a back insulating resin layer, and an intermediate insulating resin layer, respectively, 3 denotes a connecting wiring, and 4 denotes a main wiring.

[0020] In the flexible double-sided electrode sheet 5 of the present invention, as shown in FIG. 1 (plan view from the front side), any number of electrodes and wiring can be arranged in any position depending on the application.

[0021] Figure 2 shows a cross-sectional view of an example of a flexible double-sided electrode sheet of the present invention, taken along the main wiring. As shown in Figure 2, the front electrode 1a and the back electrode 1b are embedded on the front and back sides (2a and 2b) of the insulating resin sheet, respectively, at positions facing each other, with their surfaces exposed, forming a pair of electrodes (electrode pair) at roughly the same positions on the front and back. In this example, both electrodes are shaped to protrude from the sheet surface.

[0022] The front electrode 1a and the back electrode 1b are connected by a connection wiring 3 to ensure electrical continuity. A main wiring 4 is arranged extending from the back electrode 1b, and can be connected to an external detection device or the like to input and output signals. Note that in the present invention, for convenience, the front and back sides of the insulating resin sheet, the front electrode and the back electrode, etc. are described as having a front and a back, but the front and back here are not fixed and may be interchanged as needed.

[0023] Figure 3 is a cross-sectional view schematically illustrating an example of a flexible double-sided electrode sheet of the present invention similar to that shown in Figure 2. In Figure 3, P is an electrode portion, and Q is a wiring portion. The wiring portion Q includes a connection portion Q1, a main wiring portion Q2, and a sub-wiring portion Q3. The electrode portion P includes a front electrode 1a and a back electrode 1b, and its planar area is defined by the peripheries of both electrodes. The connection portion Q1 is an area including the connection wiring 3 that connects the front electrode and the back electrode.

[0024] The present invention is characterized in that the electrode portions and connection portions do not overlap within the planar region of the insulating resin sheet. For example, as shown in Figure 3, which is a cross-sectional view of an example of a flexible double-sided electrode sheet of the present invention viewed from the thickness direction, it is important that the regions of the electrode portion P and the connection portion Q1 do not overlap. In other words, when the flexible double-sided electrode sheet is viewed in plan from directly above, no connection wiring is arranged within the electrode region defined by the peripheries of the front and back electrodes. The electrodes and connection wiring are arranged so that there is no overlapping portion.

[0025] 3, the flexible double-sided electrode sheet of the present invention has a front-side insulating resin layer 2a, a back-side insulating resin layer 2b, and an intermediate insulating resin layer 2c, and in the electrode portion P, a front-side electrode 1a and a back-side electrode 1b are arranged in pairs at opposing positions on both the front and back sides of the insulating resin sheet, with the intermediate insulating resin layer 2c sandwiched between them, to form a three-layer structure. The conductive wiring (connection wiring 3) for establishing electrical connection between the front-side electrode and the back-side electrode is formed in a position slightly shifted from the region of the electrode portion P in the three-layer structure so as not to overlap with the electrode portion.

[0026] Both electrodes are embedded in the insulating resin sheet but are exposed from the surface of the insulating resin sheet. Although they do not protrude from the surface of the sheet in Fig. 3, they may be exposed in a protruding shape from the surface of the sheet as shown in Fig. 2, and preferably have a protruding shape as shown in Fig. 2. Having a protruding shape from the surface has the advantage of making it easier to detect signals and ensure continuity.

[0027] The above-mentioned FIGS. 1 to 3 are examples of the flexible double-sided electrode sheet of the present invention, and the present invention is not necessarily limited to such a structure.

[0028] 1. Insulating Resin Sheet (Base Material) (1) Resin Material The flexible double-sided electrode sheet of the present invention uses an insulating resin sheet as a base material. The insulating resin sheet has at least a front-side insulating resin layer and a back-side insulating resin layer, and preferably has an intermediate insulating resin layer between the front-side insulating resin layer and the back-side insulating resin layer.

[0029] The resin material constituting the insulating resin sheet is not particularly limited, but examples include those containing, as a main component, one or more resins selected from urethane resin, acrylic resin, vinyl chloride resin, epoxy resin, phenolic resin, polyamide resin, acrylonitrile-butadiene copolymer, polyester resin, polyimide resin, silicone resin, styrene-based block copolymer, amine compound, bismaleimide compound, etc. Among these, urethane resin, acrylic resin, silicone resin, etc. are preferred. Of these, acrylic resin is particularly preferred.

[0030] The resin material constituting the insulating resin sheet preferably contains a curing agent such as isocyanate, amine, or thiol, a photopolymerization initiator such as an alkylphenone compound or a benzophenone compound, or an organic solvent such as a glycol ether solvent, acetate solvent, alcohol solvent, ketone solvent, or ester solvent.

[0031] In addition to the above-mentioned curing agent, photopolymerization initiator, and organic solvent, optional components well known in the ink field may also be contained, such as curable monomers, colorants, surface conditioners, stabilizers, thickeners, and chelating agents.

[0032] The front-side insulating resin layer, the back-side insulating resin layer, and the intermediate insulating resin layer that constitute the insulating resin sheet may all be made of the same resin material, or may be made of one or more different resin materials. Preferably, they are all made of the same resin material.

[0033] (2) Flexibility (Pliability) The insulating resin sheet has high flexibility. For example, the 10% modulus, which is a physical property that serves as a benchmark for flexibility, preferably exhibits a value of about 1 to 10 MPa. The 10% modulus is the modulus (MPa) at an elongation of 10% measured in accordance with JIS K7311.

[0034] (3) Thickness The thickness of the insulating resin sheet is not particularly limited, but the upper limit of the thickness of the insulating resin sheet in the region where no electrodes are formed is preferably 500 μm or less, more preferably 400 μm or less, and particularly preferably 350 μm or less. In the present invention, a thin insulating resin sheet can be used. Even if the insulating resin sheet is thin, it can maintain high resistance to deformation such as bending or stretching without causing damage or falling off of the electrodes.

[0035] There is no particular lower limit to the thickness of the insulating resin sheet, but in consideration of the strength of the sheet, it is preferably 60 μm or more, more preferably 70 μm or more, and particularly preferably 80 μm or more.

[0036] In the electrode portion area of ​​the insulating resin sheet, if the electrode shape described below has a protrusion, the thickness is approximately 70 to 560 μm, and if the protrusion of the electrode is not taken into consideration, the thickness is approximately 60 to 500 μm, the same as the area where the electrode portion is not formed.

[0037] 2. Electrode Section The flexible double-sided electrode sheet of the present invention has an electrode section including a pair of electrodes arranged on the front and back sides of the insulating resin sheet.

[0038] (1) Pair of Electrodes (Electrode Pair) In the electrode portion, at least a pair of electrodes (front electrode 1a and back electrode 1b in FIG. 2 or 3) are embedded in the insulating resin sheet on the front and back sides of the insulating resin sheet so that their surfaces are exposed. The front electrode and back electrode are independently formed at opposing positions on the front and back sides of the insulating resin sheet. Therefore, the electrode pair is disposed at approximately the same position on both sides of the insulating resin sheet.

[0039] The insulating resin sheet as a whole has at least one electrode pair formed thereon, consisting of a front electrode and a back electrode. The number of electrode pairs formed can be determined appropriately depending on the application of the flexible double-sided electrode sheet of the present invention. For example, a rectangular double-sided electrode sheet can be used, in which one electrode pair is provided at one end of a strip-shaped insulating sheet in the longitudinal direction and another electrode pair is provided at the other end (a total of two electrode pairs).

[0040] (2) Exposure of Electrodes The pair of electrodes are preferably embedded in the insulating resin sheet with at least a portion thereof exposed on the surface thereof. The front electrode is disposed exposed on the front side of the insulating resin sheet. The back electrode is disposed exposed on the back side of the insulating resin sheet at approximately the same position as the front electrode (opposite the front electrode).

[0041] "Exposed" means that the surface of the electrode is not covered by anything, allowing the electrode to directly contact the test site. Note that it is sufficient that at least a part of the surface of the electrode is exposed, and the entire electrode surface may be exposed or only a part may be exposed. Preferably, the entire electrode surface is exposed.

[0042] (3) Shape of Electrode The shapes of the front electrode and the back electrode of the present invention are not particularly limited. The shape of the electrode when viewed from above can be various depending on the application and is not particularly limited, but examples thereof include a substantially circular, a substantially elliptical, a substantially rectangular, and a substantially square.

[0043] The size of the electrode when viewed from above is not particularly limited and can be determined appropriately depending on the application. In the case of a substantially circular shape, a circle with a diameter of about 1 to 50 mm is preferable. In the case of a substantially elliptical or substantially rectangular shape, a size of about 5 to 100 mm in the longitudinal direction and about 1 to 50 mm in the lateral direction is preferable. In the case of a substantially square shape, a size of about 1 to 50 mm on each side can be mentioned.

[0044] The cross-sectional shape of the electrode may be exposed on the same surface as the sheet surface or may be exposed (or protrude) from the sheet surface as shown in the cross-sectional view of Figure 2, but a protruding shape is preferred. The degree of protrusion is not particularly limited, but the distance from the apex of the protrusion to the surface of the insulating resin sheet is preferably 5 μm or more, more preferably 10 μm or more. The upper limit is not particularly limited, but is 30 μm or less, more preferably 20 μm or less.

[0045] (4) Three-Layer Structure In the present invention, the electrode portion preferably has a structure in which a front electrode and a back electrode are arranged at positions facing each other on the front and back sides of the insulating resin sheet, and an insulating resin layer is further sandwiched between the front electrode and the back electrode. When viewed in the thickness direction of the insulating resin sheet, the electrode portion preferably has a structure consisting of at least three layers including the front electrode, the back electrode, and an intermediate insulating resin layer arranged between the front electrode and the back electrode.

[0046] The structure of the electrode part is not limited to only three layers, and in addition to the three layers consisting of the front electrode, back electrode, and intermediate insulating resin layer, it may also include a surface protection layer, a shielding layer, an adhesive auxiliary layer, etc.

[0047] (5) Electrode Material The electrodes of the present invention can be formed by a known method. Examples of electrode formation methods include electrolytic plating, electroless plating, sputtering, and printing methods such as screen printing and inkjet printing. Among these, screen printing using screen ink and inkjet printing using inkjet ink are preferred.

[0048] Examples of materials constituting the electrodes include conductive materials. Examples of conductive materials include conductive compositions containing at least a conductive substance. For example, when a screen printing method is used to form the electrodes described below, a conductive ink for screen printing is used.

[0049] Examples of conductive substances include conductive metals such as gold, silver, copper, platinum, zinc, tin, palladium, aluminum, and nickel, fine particles or colloids of various alloys, inorganic conductive fine particles or oxides or chlorides such as carbon black, and conductive polymers such as PEDOT / PSS (thiophene-based conductive polymer), polyacetylene, poly(p-phenylene vinylene), polypyrrole, polythiophene, polyaniline, and poly(p-phenylene). These may be used alone or in combination of two or more.

[0050] The conductive material can be used in combination with a binder resin. As the binder resin, epoxy-based, polyester-based, polyether-based, polycarbonate-based, urethane-based, acrylic-based, isocyanate-based, or other resins can be preferably used. The binder resin may be a thermosetting type or an ultraviolet-curing type.

[0051] 3. Wiring (1) Configuration The flexible double-sided electrode sheet of the present invention has an electrode portion and a wiring portion arranged therein, and the wiring portion includes a connection portion where connection wiring is arranged, a main wiring portion where main wiring is arranged, and a sub-wiring portion where sub-wiring is arranged. The connection wiring in the connection portion serves to connect the front-side electrode and the back-side electrode, and the sub-wiring in the sub-wiring portion serves to connect the front-side electrode and the connection wiring, and the back-side electrode and the connection wiring, respectively. The front-side electrode is connected to the connection wiring through the sub-wiring, and the connection wiring is connected to the back-side electrode through the sub-wiring, thereby ensuring continuity between the front-side electrode and the back-side electrode. The main wiring in the main wiring portion extends from the front-side electrode or the back-side electrode and connects to an external detection device, etc., thereby enabling signal input and output.

[0052] The wiring portion is buried inside the insulating resin layer. That is, the connection wiring, main wiring, and sub-wiring are all disposed so as to be buried inside the insulating resin layer. The front-side electrode and the back-side electrode are connected by wiring buried inside the insulating resin layer without being exposed to the surface.

[0053] The connection wiring, main wiring, and sub-wiring are not necessarily clearly distinguished, and are usually all part of wiring made of the same material. The wiring arranged in the thickness direction to connect a pair of electrodes on the front and back sides is the connection wiring, and the area including at least this connection wiring is the connection part.

[0054] In one example of the present invention shown in Figure 3, the connection wiring 3 in the thickness direction connecting the front electrode 1a and the back electrode 1b is connected to a sub-wiring 3' extending in the planar direction from the front electrode 1a and a sub-wiring 3'' extending in the planar direction from the back electrode 1b.

[0055] On the other hand, the sub-wiring 3'' extending in the planar direction from the back-side electrode 1b further extends from the connection portion Q1 to form the main wiring 4. The main wiring 4 is included in the main wiring portion Q2. This main wiring portion Q2, the connection portion Q1 including the connection wiring 3, and the sub-wiring portion Q3 including the sub-wirings 3' and 3'' form the wiring portion Q (see FIG. 3).

[0056] In this way, the front electrode 1a and the back electrode 1b are connected by the connection wiring 3 (and the sub-wirings 3' and 3''). As a result, electrical continuity between the front electrode 1a and the back electrode 1b can be ensured via the connection wiring 3.

[0057] 3, the main wiring 4 extends from the back electrode 1b, but the main wiring 4 may extend from the front electrode 1a, or may extend from any intermediate position of the connection wiring 3. The main wiring may extend from both the front electrode and the back electrode. Multiple main wirings 4 may extend from a region including one electrode pair.

[0058] For example, in a rectangular double-sided electrode sheet having one electrode pair at one longitudinal end of a strip-shaped insulating sheet and one electrode pair at the other end (two electrode pairs in total), the front electrodes and back electrodes of the two electrode pairs are connected by main wiring, and connecting wiring is formed in the thickness direction of the sheet at an appropriate position, thereby ensuring conductivity from one electrode pair to the other electrode pair.

[0059] As such, in the present invention, it is not necessarily necessary to clearly distinguish between the connection wiring and the main and sub-wiring, but when viewed in a plan view from directly above the insulating resin sheet, it is necessary that at least the connection portion including the connection wiring is positioned away from the electrode portion area so as not to overlap with it.

[0060] Although a cross-sectional view is shown in Figure 3, the connection wiring 3 can be provided in any position around the electrodes (1a, 1b) in any shape. For example, it can be a line with the same width as the main wiring and extending from the main sub-wiring in the thickness direction of the sheet. It can also be formed in a circular shape surrounding the electrode, with the main wiring extending from any point on the circle, or it can be arranged in the shape of a part of a circle (such as a semicircle) close to the electrode, with the main wiring extending from any point on that circle.

[0061] (2) Materials The wiring (including main and sub-wirings and connection wiring) in the present invention can be formed by a known method. Examples of wiring formation methods include electrolytic plating, electroless plating, sputtering, and printing methods such as screen printing and inkjet printing. Among these, screen printing using screen ink and inkjet printing using inkjet ink are preferred.

[0062] The material constituting the wiring is preferably a conductive material. The connection wiring may be distinguished from the main sub-wiring in that it serves to connect the front electrode and the back electrode, but the connection wiring may be formed of the same conductive material or different materials. Preferably, the connection wiring and the main sub-wiring are formed of the same conductive material.

[0063] The conductive material for the wiring can be a conductive composition containing at least a conductive substance, similar to the conductive material for the electrodes. For example, when a screen printing method is used to form the electrodes and wiring described below, a conductive ink for screen printing is used.

[0064] The conductive substance may be any of the conductive materials suitable for use in the electrodes described above.

[0065] 3. Flexible Double-Sided Electrode Sheet (1) Configuration The flexible double-sided electrode sheet of the present invention is characterized in that at least the electrode portion and the connection portion do not overlap within the planar region of the insulating resin sheet. For example, in the example shown in FIG. 3 , the distance (m in FIG. 3 ) between the connection wiring side end of the electrode portion P and the electrode side end of the connection wiring 3 is preferably 100 μm or more, more preferably 300 μm or more, and particularly preferably 500 μm or more. Wiring formation techniques such as screen printing impose a minimum wiring thickness. If this distance is too short, the electrode portion P and the connection wiring 3 may overlap, potentially damaging the electrode portion due to bending or stretching. The upper limit of this distance is not particularly limited and can be determined depending on the desired shape and application of the flexible double-sided electrode sheet.

[0066] In the present invention, the connection portions are positioned away from the electrodes, and the electrode and connection portions do not overlap when the insulating resin sheet is viewed from directly above, which allows the resulting flexible double-sided electrode sheet to exhibit high resistance to bending and slight stretching, etc. If there is an overlap between the electrode and connection portions, there is a risk of breakage at that point.

[0067] A typical structure of a conventional double-sided electrode sheet is shown in Figure 5. As shown in Figure 5, in a conventional double-sided electrode sheet, the electrodes 7 on both the front and back sides are integrated and exposed on both sides of the insulating resin sheet 9, and the electrode portions and connection portions are also integrated, so that the electrodes on both the front and back sides are electrically connected within the electrode area. When viewed from directly above the double-sided electrode sheet, the electrode portions and connection portions overlap. With this type of structure, bending or stretching of the sheet can easily cause the electrode portions to break or fall off, resulting in insufficient electrical continuity.

[0068] (2) Thickness of the Flexible Double-Sided Electrode Sheet The thickness of the flexible double-sided electrode sheet of the present invention is not particularly limited, but the thickness of the flexible double-sided electrode sheet in the region where no electrode portion is formed is preferably 500 μm or less, more preferably 400 μm or less, even more preferably 350 μm or less, and particularly preferably 300 μm or less. The lower limit of the thickness is not particularly limited, but in consideration of the strength of the sheet, it is preferably 60 μm or more, more preferably 70 μm or more, even more preferably 80 μm or more, and particularly preferably 100 μm or more.

[0069] Furthermore, when the electrode has a protruding shape, the thickness of the electrode portion is preferably 560 μm or less, more preferably 460 μm or less, even more preferably 410 μm or less, and particularly preferably 360 μm or less. There is no particular lower limit to the thickness, but in consideration of the strength of the sheet, it is preferably 70 μm or more, more preferably 80 μm or more, even more preferably 90 μm or more, and particularly preferably 110 μm or more. When the protruding electrode is not taken into consideration, the thickness is about 60 to 500 μm, similar to the region where the electrode portion is not formed.

[0070] The thickness of the front-side insulating resin layer constituting the flexible double-sided electrode sheet is not particularly limited, but is preferably 10 to 120 μm, more preferably 15 to 100 μm, and particularly preferably 20 to 80 μm. The thickness of the back-side insulating resin layer is not particularly limited, but is preferably 10 to 120 μm, more preferably 15 to 100 μm, and particularly preferably 20 to 80 μm.

[0071] When an intermediate insulating resin layer is provided, the thickness of the intermediate insulating resin layer is not particularly limited, but is preferably 10 to 200 μm, more preferably 15 to 150 μm, and particularly preferably 20 to 100 μm.

[0072] In the electrode region, a three-layer structure is formed by the front electrode, the back electrode, and the intermediate insulating resin layer, and the thickness of the intermediate insulating resin layer in the electrode region can be made thicker than that in other regions. This allows both the front electrode and the back electrode to protrude from the surface of the insulating resin sheet. The thickness of the intermediate insulating resin layer in the electrode region is preferably 20 to 260 μm, more preferably 25 to 210 μm, and particularly preferably 30 to 160 μm. The difference in thickness from other regions is preferably 5 to 30 μm, more preferably 5 to 25 μm, and particularly preferably 5 to 20 μm.

[0073] The flexible double-sided electrode sheet of the present invention has a unique arrangement of electrodes and connectors, which allows the insulating resin sheet substrate to be thin and still be resistant to bending and stretching, making it possible to produce an extremely thin sheet that was difficult to achieve with conventional double-sided electrode sheets.

[0074] In conventional double-sided electrode sheets, the larger the electrode portion, the more susceptible the sheet is to breaking when bent or stretched. In the double-sided electrode sheet of the present invention, the thickness of the intermediate insulating resin layer is increased as the electrode portion becomes larger, thereby ensuring resistance to bending and stretching.

[0075] In the present invention, the ratio of [size of electrode portion exposed on the surface (mm)] / [thickness of intermediate insulating resin layer (mm)] is preferably 350 or less, and particularly preferably 333 or less. If this value is too large, that is, if the thickness of the intermediate insulating resin layer is too thin compared to the size of the electrode, the layer tends to break easily. There is no particular lower limit for the ratio of [size of electrode portion exposed on the surface (mm)] / [thickness of intermediate insulating resin layer (mm)], but it is preferably 1 or more, more preferably 10 or more, and particularly preferably 50 or more.

[0076] Here, "the size of the electrode portion exposed on the surface" refers to the length of the longest part of the shape of the exposed electrode portion when viewed from above. For example, this refers to the diameter in the case of a substantially circular shape, the longitudinal length in the case of a substantially oval or substantially rectangular shape, or the length of one side in the case of a substantially square shape. The size of the exposed electrode portion is a value measured after the electrode portion is formed on the sheet.

[0077] II. Method for manufacturing a flexible double-sided electrode sheet 1. Steps A to E The flexible double-sided electrode sheet of the present invention can be manufactured by a method including at least the following steps A to E. A: A step of forming a back-side insulating resin layer that constitutes the back side of a flexible insulating resin sheet on a release substrate B: A step of forming back-side electrodes and wiring C: A step of forming an intermediate insulating resin layer D: A step of forming front-side electrodes and wiring E: A front-side forming step of forming a front-side insulating resin layer that constitutes the front side of a flexible insulating resin sheet

[0078] <Step A> Step A is a step of forming a back-side insulating resin layer that constitutes the back side of the flexible insulating resin sheet on a release substrate. For example, as shown in Figure 4, which is an example of the manufacturing method of the present invention, in step A, a back-side insulating resin layer 2b is formed on a release substrate 6.

[0079] Any of the conventionally known release substrates can be used. Preferred examples include substrates such as paper or film on which a polyolefin film such as a polyethylene film, a polypropylene film, or a polymethylpentene film is laminated as a release layer, as well as substrates such as paper or film coated with a silicone-based or fluorine-based release agent.

[0080] The insulating resin constituting the insulating resin layer is preferably one containing, as a main component, one or more resins selected from the above-mentioned urethane resin, acrylic resin, vinyl chloride resin, epoxy resin, phenolic resin, polyamide resin, acrylonitrile-butadiene copolymer, polyester resin, polyimide resin, silicone resin, styrene-based block copolymer, amine compound, bismaleimide compound, etc.

[0081] The method for forming the insulating resin layer on the release substrate is not particularly limited, but a printing method using an insulating resin ink is preferred. Known printing methods such as gravure printing, screen printing, photolithography, gravure offset printing, xerography, stamping, flexographic printing, painting, airbrushing, and inkjet printing can be used. Among these, screen printing and inkjet printing are preferred, with inkjet printing being particularly preferred. For example, it is preferred to set a pattern in advance using an inkjet method according to the desired structure of the double-sided electrode sheet, and then inkjet-print the back-side insulating resin layer using the insulating resin ink described below.

[0082] The thickness of the back-side insulating resin layer formed in step A is not particularly limited, but when it is formed by inkjet printing using an insulating resin ink, it is adjusted to preferably 10 to 120 μm, more preferably 20 to 80 μm. After the back-side insulating resin layer is formed, it may be subjected to a drying treatment, a photocuring treatment, a heat curing treatment, or the like as necessary.

[0083] <Process B> In Process B, at least a back-side electrode is formed, and wiring is simultaneously formed as necessary. When a main wiring is extended from the back-side electrode, wiring including main and sub-wirings may be simultaneously formed in Process B. On the other hand, when a main wiring is extended from a front-side electrode, only sub-wirings may be formed in Process B.

[0084] 4 , in step B, wiring (main wiring 4) is formed on the back-side insulating resin layer 2b formed on the release substrate 6 in step A. In this case, the back-side insulating resin layer is patterned in advance in step A according to the desired structure of the double-sided electrode sheet, and it is desirable to form the back-side electrode 1b in accordance with the desired structure in an area where the back-side insulating resin layer 2b is not formed. This allows the back-side electrode to be arranged so as to be exposed on the back side of the final double-sided electrode sheet.

[0085] As a method for forming backside electrodes in areas where the backside insulating resin layer is not formed according to the desired structure of the double-sided electrode sheet, or for forming wiring in a desired arrangement, it is preferable to form a pattern in advance taking into consideration the arrangement of the electrodes and wiring.

[0086] The method for forming the backside electrode and the necessary wiring is not particularly limited, but a printing method using a conductive ink is preferred. Known printing methods, such as gravure printing, screen printing, photolithography, gravure offset printing, flexographic printing, and inkjet printing, can be used. Among these, screen printing and inkjet printing are preferred, with screen printing being particularly preferred. For example, a method is exemplified in which a screen plate with a desired pattern is set in advance, and electrodes and wiring are patterned using a known conductive ink.

[0087] The conductive ink is not particularly limited, but may be one in which a conductive substance is dissolved or dispersed in a solvent.

[0088] The thickness of the electrodes formed in step B is not particularly limited, but is preferably adjusted to 10 to 120 μm, more preferably 20 to 80 μm. The thickness of the wiring is not particularly limited, but is preferably adjusted to 10 to 40 μm, more preferably 15 to 30 μm. After the electrodes and wiring are formed, drying treatment, photocuring treatment, heat curing treatment, etc. are carried out as necessary.

[0089] <Step C> In step C, an intermediate insulating resin layer is formed on the back-side insulating resin layer, back-side electrodes, and necessary wiring formed in steps A and B. The resin material constituting the intermediate insulating resin layer may be the same as or different from that of the back-side insulating resin layer formed in step A, but preferably the same resin material as that of the back-side insulating resin layer formed in step A is used.

[0090] The method for forming the intermediate insulating resin layer is not particularly limited, but preferably includes a printing method using an insulating resin ink as in step A, and preferably screen printing or inkjet printing, particularly preferably inkjet printing. For example, it is preferable to set a pattern in advance using an inkjet method according to the desired structure of the double-sided electrode sheet, and then inkjet print the intermediate insulating resin layer using an insulating resin ink. As the insulating resin ink, preferably, the same ink as that used to form the back-side insulating resin layer can be used.

[0091] 4, in step C, an intermediate insulating resin layer 2c is formed on the back-side insulating resin layer 2b, back-side electrode 1b, and main wiring 4 formed in steps A and B. However, since the connection wiring 3 connecting back-side electrode 1b and front-side electrode 1a in the final double-sided electrode sheet is positioned away from the electrode portions, it is preferable to form a pattern of the intermediate insulating resin layer in advance, taking into consideration the placement of openings for the connection wiring, according to the desired structure of the double-sided electrode sheet, for example, so that the front-side electrode and the connection wiring formed in step D described below can be formed at a predetermined distance apart. For example, a method can be used in which a desired pattern is set in advance using an inkjet system and the intermediate insulating resin layer is formed using an insulating resin ink.

[0092] The thickness of the intermediate insulating resin layer formed in step C is not particularly limited, but when it is formed by inkjet printing using an insulating resin ink, it is adjusted to preferably 10 to 200 μm, more preferably 20 to 100 μm.

[0093] When the electrodes are formed in a protruding shape that rises from the surface of the double-sided electrode sheet as shown in Fig. 2, the thickness of the intermediate insulating resin layer at the position corresponding to the electrode portion can be increased (for example, by setting the amount of insulating resin ink to be increased in inkjet printing) in the stage of forming the intermediate insulating resin layer in step C. After the intermediate insulating resin layer is formed, drying treatment, photo-curing treatment, heat-curing treatment, etc. are performed as necessary.

[0094] <Process D> In Process D, wiring including a front-side electrode and connection wiring is formed. For example, as shown in Fig. 4, in Process D, a front-side electrode 1a is formed on the intermediate insulating resin layer formed in Process C. In this case, the front-side electrode 1a is formed in accordance with the desired structure of the double-sided electrode sheet so as to be in approximately the same position as the back-side electrode formed in Process B (arranged so as to face the back-side electrode as a pair of electrodes).

[0095] Furthermore, the connection wiring 3 is formed in the opening of the intermediate insulating resin layer formed in the above-mentioned step C. The intermediate insulating resin layer is patterned in advance in the above-mentioned step C according to the desired structure of the double-sided electrode sheet, and according to this desired structure, the connection wiring 3 can be formed in the thickness direction in the portion (opening) where the intermediate insulating resin layer 2c is not formed so that it is positioned a predetermined distance from the front-side electrode 1a. At the same time, a sub-wiring 3' that connects the thickness-wise connection wiring 3 and the front-side electrode 1a can be formed on the intermediate insulating resin layer.

[0096] The connection wiring 3 formed in the thickness direction is formed in the opening of the intermediate insulating resin layer formed in the above-mentioned step C, and can simultaneously be connected to the main wiring 4 formed in step B. As a result, the front-side electrode 1a and the back-side electrode 1b are connected via the sub-wiring 3' to the connection wiring 3, and then from the connection wiring 3 to the main wiring 4' (= sub-wiring 3''), and as a result, electrical continuity between the front-side electrode 1a and the back-side electrode 1b can be ensured via the connection wiring 3.

[0097] The main wiring 4' is the same as the sub-wiring 3'' in Figure 3 and is both a main wiring and a sub-wiring. In this example, the main wiring 4 extends from the back-side electrode 1b, but the main wiring 4 may extend from the front-side electrode 1a, or may extend from both the front-side electrode 1a and the back-side electrode 1b, or may have a structure in which it extends from any intermediate position of the connection wiring 3.

[0098] The connection wiring 3 is formed at a position away from the front-side electrode. As for the distance from the front-side electrode, for example, the length of the sub-wiring 3' and / or sub-wiring 3'' connecting the connection wiring 3 and the front-side electrode 1a is preferably 100 μm or more, more preferably 300 μm or more, and particularly preferably 500 μm or more. There is no particular upper limit to this distance, and it can be determined depending on the desired shape and application of the flexible double-sided electrode sheet.

[0099] When the main wiring is extended from the front electrode (the connection wiring 3' in FIG. 4 is also the main wiring 4), the main wiring 4 can be formed in step D instead of step B.

[0100] As a method for forming the front electrodes according to the desired structure of the double-sided electrode sheet, or for forming connecting wiring in the part where the intermediate insulating resin layer is not formed and connecting it to the front electrodes, it is preferable to form a pattern in advance taking into consideration the arrangement of the electrodes and wiring.

[0101] The method for forming the front electrodes and connection wiring is not particularly limited, but as in step B, screen printing, inkjet printing, etc. are preferred, and screen printing is particularly preferred. For example, there is a method in which a screen plate with a desired pattern is set in advance and a known conductive ink is used to form a pattern of electrodes and wiring. The conductive ink used is the same as the conductive ink used in step B.

[0102] <Step E> In step E, a front-side insulating resin layer that constitutes the front side of the flexible double-sided electrode sheet of the present invention is formed on the intermediate insulating resin layer and wiring (connection wiring 3') formed in steps C and D. The resin material that constitutes the front-side insulating resin layer may be the same as or different from the resin material of the back-side insulating resin layer formed in step A and / or the intermediate insulating resin layer formed in step C, but preferably the same resin material is used as at least one of the back-side insulating resin layer and the intermediate insulating resin layer. More preferably, the back-side insulating resin layer, the intermediate insulating resin layer, and the front-side insulating resin layer are all made of the same resin material.

[0103] The method for forming the surface-side insulating resin layer is not particularly limited, but preferably includes a printing method using an insulating resin ink as in steps A and C, and preferably screen printing or inkjet printing, particularly preferably inkjet printing, is used. For example, it is preferable to set a pattern in advance using an inkjet method according to the desired structure of the double-sided electrode sheet, and then inkjet print the surface-side insulating resin layer using an insulating resin ink. More preferably, the same insulating resin ink as used in steps A and C is used.

[0104] 4, in step E, a front-side insulating resin layer 2a is formed on the intermediate insulating resin layer 2c and the connection wiring 3' formed in steps C and D. However, since it is sufficient that at least the wiring (in this case, the connection wiring 3') is buried, an insulating resin layer does not need to be provided in areas where there is no risk of the wiring being exposed. Also, as shown in FIG. 4, since the front-side electrode 1a is arranged so as to be exposed on the surface of the double-sided electrode sheet, the front-side insulating resin layer 2a is not formed on the front-side electrode.

[0105] As a method for forming the surface-side insulating resin layer only in the necessary portions according to the desired structure of the double-sided electrode sheet, it is preferable to form a pattern in advance taking into consideration the arrangement of electrodes and wiring. The method for forming the surface-side insulating resin layer into the desired pattern is not particularly limited, but as with step A or step C, screen printing, inkjet printing, etc. are preferred, and inkjet printing is particularly preferred. For example, there is a method in which the desired pattern is set in advance using an inkjet method and the surface-side insulating resin layer is formed using an insulating resin ink. The insulating resin ink used is the same as the insulating resin ink used in step A and / or step C.

[0106] The thickness of the front-side insulating resin layer is not particularly limited, but when it is formed by inkjet printing using an insulating resin ink, it is adjusted to preferably 10 to 120 μm, more preferably 20 to 80 μm. After forming the back-side insulating resin layer, drying treatment, photocuring treatment, heat curing treatment, etc. are performed as necessary.

[0107] After step E, the release substrate is peeled off to obtain the flexible double-sided electrode sheet of the present invention.

[0108] The manufacturing method of the flexible double-sided electrode sheet of the present invention includes steps A to E described above, but this is merely an example, and the manufacturing method of the flexible double-sided electrode sheet of the present invention is not limited thereto. Also, Figure 4 merely schematically illustrates one example of the manufacturing method of the present invention. For example, when forming a pattern by printing using an insulating resin ink or a conductive ink, the ink has a certain degree of fluidity, so it is not necessary to form a pattern with clear corners as shown in Figures 3 and 4 . The corners of the shapes of openings, electrodes, wiring, etc. may be curved (radial), or a rectangle may be a trapezoid or lens shape.

[0109] Furthermore, the thickness of each layer does not necessarily have to be constant as shown in Figures 3 and 4. For example, when printing using a fluid ink in each process, the entire sheet can be smoothed by a leveling process or the like after forming the resin layer, electrodes, wiring, etc. In this case, the insulating resin layers on the front, middle, back, etc. sides do not necessarily have a constant thickness across the entire double-sided electrode sheet as shown schematically in Figure 3, and there may be places where the thickness is relatively thicker or thinner depending on the formation positions of the electrodes and wiring, etc.

[0110] 2. Insulating Resin Ink Examples of insulating resin inks (hereinafter simply referred to as "inks") suitable for use in inkjet printing in the above process include those containing optional components such as solvents, binder resins, and other known additives used in inks, as needed.

[0111] As the binder resin, resins such as epoxy, urethane, vinyl chloride, silicone, phenol, polyamide, polyester, acrylic, and isocyanate can be used. The binder resin may be a thermosetting type or an ultraviolet-curing type. An ultraviolet-curing resin is preferably used. In the case of an ultraviolet-curing resin, a photopolymerization initiator is also contained.

[0112] Examples of thermosetting binder resins include epoxy resins, urethane resins, and carboxylic acid acrylic polymers. Examples of epoxy resins include bisphenol A liquid epoxy resins, cresol novolac epoxy resins, and phenol novolac epoxy resins. Examples of urethane resins include resins obtained by reacting polyols with polyisocyanates. Commercially available epoxy resins, urethane resins, and carboxylic acid acrylic polymers can be used as appropriate.

[0113] Examples of ultraviolet-curable binder resins include ultraviolet-curable oligomers such as urethane-based, acrylic-based, polycarbonate-based, epoxy-based, polyether-based, and polyester-based oligomers having two or more photopolymerizable functional groups in one molecule.

[0114] <UV-Curable Oligomer> Among UV-curable oligomers, polyfunctional urethane-based oligomers include those obtained by reacting a polyol with an organic polyisocyanate to prepare a urethane prepolymer, and then reacting the urethane prepolymer with a hydroxyl group-containing (meth)acrylate. Alternatively, the urethane-based oligomer may be obtained by reacting an organic polyisocyanate with a hydroxyl group-containing (meth)acrylate.

[0115] Examples of the acrylic oligomer include polymers of alkyl (meth)acrylates such as (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate; and copolymers of the above monomers with compounds selected from vinyl carboxylic acid compounds such as maleic acid, itaconic acid, crotonic acid, and fumaric acid; glycidyl group-containing vinyl compounds such as glycidyl (meth)acrylate, allyl glycidyl ether, ethyl glycidyl acrylate, crotonyl glycidyl ether, and glycidyl crotonate; hydroxyethyl (meth)acrylate, vinyl acetate, (meth)acrylonitrile, (meth)acrylic acid chloride, and N-(meth)acryloylmorpholine.

[0116] Examples of polycarbonate oligomers include oligomers obtained by reacting polycarbonate polyol, polyisocyanate, and hydroxy-functional ethylenically unsaturated monomers.

[0117] Examples of epoxy oligomers include epoxy oligomers obtained by reacting epoxy resins with acrylates. Examples of polyether oligomers include esters of polypropylene glycol and acrylic acid. Examples of polyester oligomers include esters of acrylic acid and polyester diols made from adipic acid and 1,6-hexanediol.

[0118] Among these, the ultraviolet-curable oligomer is preferably a urethane-based oligomer, since the coating film obtained after curing has excellent flexibility.

[0119] <Solvent> The solvent is not particularly limited, but water or an organic solvent is used. When an ultraviolet-curable oligomer is used in the ink, an organic solvent is blended as a liquid component for dissolving the ultraviolet-curable oligomer. The type of organic solvent is not particularly limited, but examples include glycol ether-based solvents, acetate-based solvents, alcohol-based solvents, ketone-based solvents, ester-based solvents, hydrocarbon-based solvents, fatty acid ester-based solvents, and aromatic solvents. The organic solvents may be used in combination.

[0120] Of these, the organic solvent used in the present invention preferably contains at least one of a glycol ether-based solvent and an acetate-based solvent, and the ink more preferably contains a glycol ether-based solvent.

[0121] Glycol ether solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono(iso)propyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and triethylene glycol monomethyl ether. Examples of the ethylene glycol dimethyl ether include diethylene glycol mono-n-propyl ether, triethylene glycol mono-n-butyl ether, tripropylene glycol monoethyl ether, tripropylene glycol mono-n-propyl ether, tripropylene glycol mono-n-butyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl methyl ether, dipropylene glycol dimethyl ether, and tripropylene glycol dimethyl ether.

[0122] Acetate solvents include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether acetate, ethylene glycol mono-n-butyl ether acetate, ethylene glycol mono-sec-butyl ether acetate, ethylene glycol monoisobutyl ether acetate, ethylene glycol mono-tert-butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monoisopropyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol mono-n-butyl ether acetate, propylene glycol mono-sec ...sec-butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monoisopropyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol mono-sec-butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monopropyl ether Examples include alkylene glycol monoalkyl ether acetates such as propylene glycol monoisobutyl ether acetate, propylene glycol mono-tert-butyl ether acetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-ethoxybutyl acetate, 3-methyl-3-propoxybutyl acetate, 3-methyl-3-isopropoxybutyl acetate, 3-methyl-3-n-butoxyethyl acetate, 3-methyl-3-isobutoxybutyl acetate, 3-methyl-3-sec-butoxybutyl acetate, and 3-methyl-3-tert-butoxybutyl acetate, ethylene glycol diacetate, diethylene glycol diacetate, triethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, and tripropylene glycol diacetate.

[0123] <Photopolymerization initiator> When an ink containing an ultraviolet-curable oligomer is used, a photopolymerization initiator is contained in order to appropriately cure the ink by ultraviolet light. The photopolymerization initiator is not particularly limited, but examples thereof include alkylphenone compounds, benzophenone compounds, benzoin compounds, thioxanthone compounds, halomethylated triazine compounds, halomethylated oxadiazole compounds, biimidazole compounds, oxime ester compounds, titanocene compounds, benzoic acid ester compounds, and acridine compounds. The photopolymerization initiator may be used in combination.

[0124] Examples of alkylphenone compounds include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone.

[0125] Examples of the benzophenone compounds include benzophenone, 4,4'-bis(dimethylamino)benzophenone, and 2-carboxybenzophenone.

[0126] Examples of the benzoin compounds include benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

[0127] Examples of thioxanthone compounds include thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, and 2,4-diethylthioxanthone.

[0128] Examples of halomethylated triazine compounds include 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-sec-triazine, 2-(4-methoxynaphthyl)-4,6-bis(trichloromethyl)-sec-triazine, 2-(4-ethoxynaphthyl)-4,6-bis(trichloromethyl)-sec-triazine, and 2-(4-ethoxycarboxynylnaphthyl)-4,6-bis(trichloromethyl)-sec-triazine.

[0129] Examples of halomethylated oxadiazole compounds include 2-trichloromethyl-5-[β-(2'-benzofuryl)vinyl]-1,3,4-oxadiazole, 2-trichloromethyl-5-[β-(2'-(6"-benzofuryl)vinyl)]-1,3,4-oxadiazole, and 2-trichloromethyl-5-furyl-1,3,4-oxadiazole.

[0130] Examples of biimidazole compounds include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, and 2,2'-bis(2,4,6-trichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole.

[0131] Examples of the oxime ester compounds include 1-[4-(phenylthio)-, 2-(O-benzoyloxime)]-1,2-octanedione, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime)ethanone, and the like.

[0132] Examples of titanocene compounds include bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium.

[0133] Examples of the benzoate ester compounds include p-dimethylaminobenzoic acid, p-diethylaminobenzoic acid, etc. Examples of the acridine compounds include 9-phenylacridine, etc.

[0134] The content of the photopolymerization initiator in the ink is not particularly limited, but is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. Furthermore, the content of the photopolymerization initiator in the ink is preferably 15% by mass or less, and more preferably 12% by mass or less. By keeping the content of the photopolymerization initiator within the above range, the ink is easily cured appropriately by ultraviolet light.

[0135] <Optional Components> In addition to the above-mentioned UV-curable oligomer, photopolymerization initiator, and organic solvent, the insulating resin ink of the present invention may contain optional components well known in the field of inks, such as reactive monomers, curing agents such as isocyanates, amines, and thiols, colorants, surface conditioners, stabilizers, and the like, which are commonly used in inks, if necessary.

[0136] The viscosity of the insulating resin ink used in the present invention is not particularly limited, but in the case of an inkjet ink, the viscosity at 25° C. is preferably 1 mPa·s or more, more preferably 5 mPa·s or more. There is no particular upper limit to the viscosity of the ink at 25° C., but it is preferably 30 mPa·s or less, more preferably 25 mPa·s or less.

[0137] 3. Conductive Ink The conductive ink is not particularly limited, but examples thereof include a conductive ink in which a conductive substance is dissolved or dispersed in a solvent. When printing by a screen printing method, a known conductive ink may be used.

[0138] Examples of conductive substances include conductive metals such as gold, silver, copper, platinum, zinc, tin, palladium, aluminum, and nickel, fine particles or colloids of various alloys, inorganic conductive fine particles or oxides or chlorides such as carbon black, and conductive polymers such as PEDOT / PSS (thiophene-based conductive polymer), polyacetylene, poly(p-phenylene vinylene), polypyrrole, polythiophene, polyaniline, and poly(p-phenylene). These may be used alone or in combination of two or more.

[0139] The conductive material can be used in combination with a binder resin. Examples of the binder resin that can be used include epoxy, polyester, acrylic, and isocyanate resins. The binder resin may be a thermosetting type or an ultraviolet-curing type. An ultraviolet-curing resin is preferably used. In the case of an ultraviolet-curing resin, a photopolymerization initiator is also contained.

[0140] The viscosity of the conductive ink used in the present invention is not particularly limited, but is preferably in the viscosity range of general screen inks, inkjet inks, etc. Specifically, in the case of screen inks, the viscosity at 25°C is 1 Pa·s or more, more preferably 5 Pa·s or more, and the upper limit of the viscosity at 25°C is not particularly limited, but is preferably 100 Pa·s or less, more preferably 80 Pa·s or less. In the case of inkjet inks, the viscosity at 25°C is preferably 1 mPa·s or more, more preferably 5 mPa·s or more, and the upper limit of the viscosity at 25°C is not particularly limited, but is preferably 30 mPa·s or less, more preferably 25 mPa·s or less.

[0141] The present invention will be described below with reference to examples, but the present invention is not limited to these examples in any way.

[0142] Example 1 Preparation of insulating resin ink 1 Insulating resin ink 1 was prepared by mixing 14 parts of a bifunctional aliphatic urethane acrylate oligomer (manufactured by Arkema K.K.; trade name "CN996"), 1 part of a bifunctional aliphatic urethane acrylate oligomer (manufactured by Arkema K.K.; trade name "CN981"), 24 parts of a blocked isocyanate (manufactured by Asahi Kasei Corporation; trade name "Duranate E402-B80B"), 12 parts of 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.; trade name "4-HBA"), 46.7 parts of 2-(allyloxymethyl)methyl acrylate (manufactured by Nippon Shokubai Co., Ltd.; trade name "AOMA"), 2 parts of 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM RESINS; trade name "Omnirad 184"), and 30 parts of diethylene glycol diethyl ether (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The viscosity of this product at 25°C was 14 mPa·s.

[0143] <Preparation of double-sided electrode sheet> A flexible double-sided electrode sheet as shown in Figures 6 and 7 was prepared by the following steps. Figure 6 is a schematic plan view (appearance) of the prepared double-sided electrode sheet as viewed from above. Figure 7 is a schematic cross-sectional view thereof. (Step A) An insulating resin ink was applied by inkjet printing onto a release paper measuring 50 mm in length and 200 mm in width (manufactured by Lintec Corporation; product name "Koteishi EV130TPD") while irradiating it with ultraviolet light, to form a patterned coating film having two 10 mm x 10 mm (square) electrode openings.

[0144] The two electrode openings were formed so that the distance from the inner edge of one square to the inner edge of the other square was 100 mm along the longitudinal direction of the sheet. The inner edges are the sides where the two electrode openings face each other with a 100 mm gap. In addition, a groove (width 1 mm × length 100 mm × depth 15 μm) for the main wiring connecting the two electrode openings was formed between the two electrode openings on the surface of the coating film opposite the release paper side.

[0145] After the coating film was formed, it was thermally cured at 130° C. for 20 minutes to form a ribbon-shaped back surface insulating resin layer measuring 20 mm×130 mm×30 μm thick, with two electrode openings spaced 100 mm apart.

[0146] (Step B) On the back surface side insulating resin layer formed in Step A, two back surface electrodes (10 mm × 10 mm; square) and a main wiring (width 1 mm × length 100 mm) were pattern-printed by screen printing using a conductive silver paste ink (manufactured by Nagase EMS Co., Ltd.; product name "CI-1036", viscosity 15 Pa s).

[0147] The two rear electrodes were printed so as to be formed within the two 10 mm × 10 mm (square) electrode openings formed in process A. The main wiring was printed so as to be formed within the main wiring groove (width 1 mm × length 100 mm × depth 15 μm) formed in process A so as to connect the two rear electrodes together.

[0148] Thereafter, the substrate was thermally cured at 130°C for 5 minutes, thereby forming two back electrodes with a thickness of 30 μm inside each of the two electrode openings, and a main wiring (width 1 mm × length 100 mm × thickness 15 μm) connecting the two back electrodes was formed in the groove for the main wiring.

[0149] Since the back-side electrodes are formed through the back side of the back-side insulating resin layer, the back-side electrodes are exposed on the surface of the back-side insulating resin layer after the release paper is removed. On the other hand, the main wiring is formed on the surface of the back-side insulating resin layer opposite to the release paper side, and is not exposed on the surface of the back-side insulating resin layer even after the release paper is removed.

[0150] (Step C) An intermediate insulating resin layer coating was formed by inkjet coating the insulating resin ink 1 onto the back-side insulating resin layer, back-side electrode, and main wiring formed in steps A and B while irradiating with ultraviolet light. A patterned coating was formed on the main wiring, completely covering the back-side electrode, and 40 mm from the inner edge of one electrode portion along the longitudinal direction of the sheet, with a 1 mm wide x 5 mm long x 30 μm deep opening for connection wiring along the main wiring. The opening for connection wiring penetrated from the top to the bottom of the coating.

[0151] The openings for connection wiring were formed along the main wiring formed along the longitudinal direction of the sheet, and the distance from the inner edge of the electrode portion to the electrode-side edge of the opening for connection wiring was 40 mm. Here, the width of the opening for connection wiring refers to the line width of the opening for connection wiring in the short direction when the rectangular double-sided electrode sheet is viewed in plan, and the length of the opening for connection wiring refers to the length along the longitudinal direction of the sheet. After forming the coating film, it was thermally cured at 130°C for 20 minutes to form an intermediate insulating resin layer with a thickness of 30 μm.

[0152] (Step D) Using a conductive silver paste ink (manufactured by Nagase EMS Co., Ltd.; product name "CI-1036"), two 10 mm x 10 mm (square) surface-side electrodes, a connecting wire 1 mm wide x 5 mm long, and a main wire 1 mm wide x 100 mm long x 15 μm thick connecting the two surface-side electrodes were pattern-printed by a screen printing method on the intermediate insulating resin layer formed in step C.

[0153] At this time, the two front-side electrodes were printed in such a manner that their positions were approximately the same as those of the two back-side electrodes formed in step B. Furthermore, the connecting wiring was printed in such a manner that it would connect the main wiring connecting the two front-side electrodes to the main wiring connecting the two back-side electrodes formed in step B through an opening measuring 1 mm wide x 5 mm long x 30 μm thick that had been formed in the intermediate insulating resin layer in step C.

[0154] The laminate was then thermally cured at 130°C for 5 minutes to form two 30µm-thick front-side electrodes (10mm x 10mm; square), a 1mm-wide, 100mm-long, 15µm-thick main wiring, and a 1mm-wide, 5mm-long, 30µm-high (depth) connection wiring. The connection wiring was connected to the main wiring formed in the back-side insulating resin layer and the main wiring formed in the front-side insulating resin layer, and each main wiring was connected to the back-side electrode and the front-side electrode, so that the front-side electrode and the back-side electrode were electrically connected via the main wiring and the connection wiring.

[0155] (Step E) Insulating resin ink 1 was applied by inkjet printing while irradiating ultraviolet light onto the intermediate insulating resin layer, surface-side electrodes, main wiring, and connection wiring formed in steps C and D, to form a coating film for the surface-side insulating resin layer. At this time, the coating film was patterned so that the surface of the surface-side electrodes formed in step D was exposed, but the other areas were completely covered with ink, with the coating film positioned accordingly. After the coating film was formed, it was thermally cured at 130°C for 20 minutes to form a surface-side insulating resin layer with a thickness of 30 μm.

[0156] The release paper was then removed, yielding the double-sided electrode sheet shown in Figures 6 and 7. The resulting double-sided electrode sheet was a 90-µm-thick flexible double-sided electrode sheet having an electrode section with electrode pairs (10 mm x 10 mm x 30 µm thick; square) consisting of two pairs of front-side electrodes 1a and back-side electrodes 1b, two main wires 4 (1 mm wide x 100 mm long x 15 µm thick) formed on the front-side insulating resin layer 2a and the back-side insulating resin layer 2b, respectively, connecting the two pairs of electrodes, and a connection wire 3 connecting the two main wires in the thickness direction. The distance between the inner end of one electrode pair and the electrical pair-side end of one of the connection wires 3 (the distance between the electrode pair and the connection wire) was 40 mm.

[0157] Example 2 A double-sided electrode sheet was produced in the same manner as in Example 1, except that the thickness of the intermediate insulating resin layer 2c was changed to 50 μm.

[0158] Example 3 A double-sided electrode sheet was produced in the same manner as in Example 1, except that the thickness of the intermediate insulating resin layer 2c was changed to 100 μm.

[0159] Example 4 A double-sided electrode sheet was produced in the same manner as in Example 1, except that the thickness of the intermediate insulating resin layer 2c was changed to 200 μm.

[0160] Example 5 A double-sided electrode sheet was produced in the same manner as in Example 1, except that the electrodes 1a and 1b were changed to a substantially circular shape of 4 mm x 4 mm.

[0161] Example 6 A double-sided electrode sheet was produced in the same manner as in Example 5, except that the thickness of the intermediate insulating resin layer 2c was changed to 20 μm.

[0162] Example 7 A double-sided electrode sheet was produced in the same manner as in Example 1, except that the main wiring 4 was changed to a width of 200 μm and a length of 15 mm, the electrodes 1 a and 1 b were changed to a substantially circular shape of 1.5 mm × 1.5 mm, and the distance between the electrode pair and the connection wiring 3 was changed to 3 mm.

[0163] Example 8 Preparation of insulating resin ink 2 Insulating resin ink 2 was obtained by mixing 20 parts of a bifunctional aliphatic urethane acrylate oligomer (manufactured by Arkema K.K.; trade name "CN996"), 67.7 parts of 2-(allyloxymethyl)methyl acrylate (manufactured by Nippon Shokubai Co., Ltd.; trade name "AOMA"), 10 parts of 1,4-bis(3-mercaptobutyryloxy)butane (manufactured by Resonac Corporation; trade name "Karenz MT BD-1"), and 2 parts of 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM ResinS; trade name "Omnirad 184")

[0164] <Preparation of double-sided electrode sheet> (Process A) The insulating resin ink 2 was applied onto a release paper (manufactured by Lintec Corporation; product name "Koteishi EV130TPD") by inkjet printing while irradiating it with ultraviolet light to form a pattern of a substantially circular coating film with an electrode opening of 1.5 mm x 1.5 mm, and a back-side insulating resin layer with a thickness of 30 μm was formed. A double-sided electrode sheet was prepared in the same manner as in Example 7, except that the intermediate insulating resin layer and the back-side insulating resin layer were also formed with insulating resin ink 2.

[0165] Example 9 A double-sided electrode sheet was produced in the same manner as in Example 1, except that the distance between the electrode pair and the connecting wiring was changed to 100 μm.

[0166] Example 10 A double-sided electrode sheet was produced in the same manner as in Example 5, except that the distance between the electrode pair and the connecting wiring was changed to 100 μm.

[0167] Example 11 A double-sided electrode sheet was produced in the same manner as in Example 1, except that in step C, the thickness of the intermediate insulating resin layer at the position corresponding to the electrode portion was made 20 μm thicker than the surrounding area to raise the electrode portion.

[0168] Comparative Example 1 A double-sided electrode sheet was produced in the same manner as in Example 5, except that step C was not performed and an intermediate insulating resin layer was not formed.

[0169] Comparative Example 2 A double-sided electrode sheet was produced in the same manner as in Example 5, except that in step C, the size of the opening for the connection wiring was set to 1 mm wide x 1 mm long x 30 μm deep, and the intermediate insulating resin layer was patterned at positions corresponding to the centers of each of the two approximately circular electrode pairs so that its formation position was at the center of the circle of the approximately circular electrode measuring 4 mm x 4 mm. In this sheet, the connection wiring extending directly from the center of the circle of the front electrode was directly connected to the center of the circle of the back electrode, providing electrical conduction.

[0170] The obtained double-sided electrode sheet had two pairs of electrodes, each of which was formed on either end of the main wiring, with the centers of the substantially circular front and back electrodes connected by a connecting wire, and the connecting wires and the electrode pairs completely overlapped when viewed from above. Also, the connecting portion Q1 and the electrode portion P in the cross-sectional view of Figure 3 overlapped.

[0171] The methods for evaluating various physical properties in the present examples are as follows. The evaluation results are shown in Tables 1 and 2. <Modulus of insulating resin sheet> Using each insulating resin ink, a dumbbell-shaped insulating resin sheet with a width of 5 to 25 mm, a length of 100 mm, and a thickness of 60 μm was prepared, and the modulus (MPa) at an elongation of 10% was measured in accordance with JIS K7311.

[0172] <Conduction between front electrode and back electrode> For each double-sided electrode sheet prepared in each example and comparative example, the resistance between the front electrode and back electrode was measured to confirm conductivity. The resistance was measured using a digital multimeter PM3 manufactured by Sanwa Electric Instruments Co., Ltd.

[0173] <Stretching durability> The double-sided electrode sheets produced in each example and comparative example were evaluated for stretching durability using a stretching durability evaluation device manufactured by Seiren Co., Ltd. as follows. First, both longitudinal ends of the ribbon-shaped double-sided electrode sheet were gripped and stretched by 10% in the length direction of the main wiring at a speed of 10 mm / s. After maintaining this for 60 seconds, the sheet was returned to its original length at a speed of 10 mm / s. Then, the presence or absence of breakage in the electrode portion of the double-sided electrode sheet was visually evaluated. ◯: No scratches or breakage ×: Breakage

[0174] <Rate of change in resistance value before and after elongation durability evaluation> The resistance value between the electrode pair and the connecting wiring (between 100 mm or 15 mm) before the elongation durability evaluation was measured, and this was designated as the initial resistance value. Then, after the elongation durability evaluation was performed, the resistance value between the electrode pair and the connecting wiring (between 100 mm or 15 mm) was measured again, and the rate of change from the initial resistance value was calculated and evaluated. A digital multimeter PM3 manufactured by Sanwa Electric Instruments Co., Ltd. was used to measure the resistance value. ◯: Resistance value change is less than 1000% △: Resistance value change is 1000% or more but less than 2000% ×: Resistance value change is 2000% or more -: Measurement not possible due to breakage

[0175]

[0176]

[0177] The flexible double-sided electrode sheet of the present invention has an electrode pair disposed at opposing positions on both sides of an insulating resin sheet, and the connection (conduction) of the electrode pair is ensured by a connection portion provided at a position away from the electrode portions. With this structure, even when the sheet is bent or stretched, the electrode portions are not damaged or removed, and high conductivity is maintained.

[0178] The flexible double-sided electrode sheet of the present invention is suitable for use as a bioelectrode in close contact with the skin of the human body to detect biosignals, or for ensuring the conductivity of moving parts in various industries such as the environmental and architectural fields. It can also be suitably used as an electrode for the examination and treatment of organs such as the heart.

[0179] 1a: Front electrode 1b: Back electrode 2a: Front insulating resin layer 2b: Back insulating resin layer 2c: Intermediate insulating resin layer 3: Connection wiring 3': Sub-wiring 3'': Sub-wiring 4: Main wiring 4': Main wiring 5: Flexible double-sided electrode sheet 6: Release substrate P: Electrode portion Q: Wiring portion Q1: Connection portion Q2: Main wiring portion Q3: Sub-wiring portion 7: Electrode 8: Wiring 9: Insulating resin

Claims

1. A flexible double-sided electrode sheet comprising at least a flexible insulating resin sheet, an electrode portion including a pair of electrodes embedded in opposing positions on the front and back sides of the insulating resin sheet so that their surfaces are exposed, and a connection portion including connection wiring embedded in the insulating resin sheet and connecting the pair of electrodes, wherein the electrode portion and the connection portion do not overlap within the planar area of ​​the insulating resin sheet.

2. The flexible double-sided electrode sheet according to claim 1, wherein the pair of electrodes are arranged on the front and back sides of the insulating resin sheet with at least a portion of the electrodes exposed.

3. The flexible double-sided electrode sheet according to claim 1, wherein the electrode portion has a structure consisting of at least three layers including a front electrode, a back electrode, and an intermediate insulating resin layer disposed between the front electrode and the back electrode.

4. The flexible double-sided electrode sheet according to claim 1, wherein the thickness of said flexible insulating resin sheet is 560 μm or less, and the thickness of said intermediate insulating resin layer is 260 μm or less.

5. The flexible double-sided electrode sheet according to claim 4, wherein the length (mm) of the electrode portion / thickness (mm) of the intermediate insulating resin layer is 350 or less.

6. The flexible double-sided electrode sheet according to claim 1, wherein said flexible insulating resin sheet is made of an acrylic resin.

7. The flexible double-sided electrode sheet according to claim 1, wherein at least the electrodes and connecting wires are formed from a conductive material containing silver.

8. A method for producing a flexible double-sided electrode sheet according to any one of claims 1 to 7, comprising at least the following steps A to E: A: a step of forming a back-side insulating resin layer that constitutes the back side of the flexible insulating resin sheet on a release substrate; B: a step of forming back-side electrodes and wiring; C: a step of forming an intermediate insulating resin layer; D: a step of forming front-side electrodes and wiring; and E: a front-side forming step of forming a front-side insulating resin layer that constitutes the front side of the flexible insulating resin sheet.

9. The method for producing a flexible double-sided electrode sheet according to claim 8, wherein steps A to E are steps of forming a pattern by screen printing or inkjet printing.

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